This invention relates to an expandable scaffold for use with hoppers and the like. In many applications hoppers are used for transportation and storage of fluid and fluid like materials. Many of these hoppers have a narrow or confined opening at the top to allow passage of the fluid material inside and then open outwards into a larger area beneath the opening. These hoppers need periodic maintenance and repair often requiring that an individual enter the hopper to work on the interior walls. It will be appreciated that working inside the hopper is very difficult and in many cases a scaffold is needed for the operator to be able stand in a suitable location when working on the interior walls.
Various scaffolds for use in vessels with restricted openings and other folding devices are shown in the prior art.
G. Johnson shows in U.S. Pat. No. 1,090,856, Mar. 24, 1914 shows a scaffold for building shells of blast furnaces or other tubular furnaces and the like. It has a hollow cylindrical central guide support which is supported by a large overhead hoist or pulley. A large cage extends outwards from the central support for a workman to stand upon. This device is not expandable and would not fit through the restricted opening in the top of a hopper.
Gladville shows in U.S. Pat. No. 2,221,133, Nov. 12, 1949 a scaffold for use with a cylindrical structure. This device is for use with a structure having a large opening at the top and would not be usable with a hopper having a restricted opening.
J. M. Titzel shows in U.S. Pat. No. 3,166154, Jan. 19, 1965 a portable scaffold work tower. The work tower is a very large self supporting tower with fixed arms at its base for use in steel making vessels. The tower is lowered into the vessel by a crane and supported on the base of the vessel by feet. The tower has a cage for lowering the workman into the vessel and outwardly extending arms at its base to support the workman.
T. Gregord shows in U.S. Pat. No. 3,454,133, Jul. 8, 1969 a portable work tower for use in vessels having limited clearance. The work tower is a very large self-supporting tower with fixed arms at its base for use in steel making vessels. The tower is lowered into the vessel in pieces and assembled in place.
Martin shows in U.S. Pat. No. 4,095,670, Jun. 20, 1978 a foldable platform for raise drilling. The platform is for lowering into a predrilled mine shaft for supporting workmen who are widening the shaft. This platform is very large and is supported by a large overhead crane. It has a central tower and foldable support arms which project out from the bottom end of the tower.
Peterman shows in U.S. Pat. No. 3,994,365, Nov. 30, 1976 an apparatus for positioning a person within a very large container tank. The apparatus is supported by a large overhead crane and is lowered into the tank through a restricted opening. The apparatus includes a central column having arms pivotally fixed to it at one end of the arms is a cage for supporting a man and at the other a counter weight.
Although these scaffolds are expandable all are either very large, expensive, require assembly with in the vessel, or would not work with a rail hopper or the like.
Calderaro shows in U.S. Pat. No. 4,168,052, Sep. 18, 1979 a foldable bearer structure for inner mould placement for use with concrete moulds and the like. Although foldable it would not be usable for the purpose desired within a hopper since it would require several men to expand it after lowering it in place within the hopper which is not practical, and is not be usable to support a man.
A scaffold is needed therefore which can fold up to pass through a narrow or confined opening and can then readily expand into a position in the interior of the hopper thereby providing the operator with a place to stand while working.